Revert "Fix Uri.Host for IPv6 Link-local address (#29829)"

[caesar-chen]

This reverts commit f7a8cf1, which regressed ASP.NET. (https://github.com/dotnet/corefx/issues/28863#issuecomment-393993963)

We need to reconsider how to solve #28863

[caesar-chen]

@dotnet-bot test Outerloop Windows x64 Debug Build
@dotnet-bot test Outerloop Linux x64 Debug Build
@dotnet-bot test Outerloop NETFX x86 Debug Build
@dotnet-bot test Outerloop UWP CoreCLR x64 Debug Build
@dotnet-bot test Outerloop Linux x64 Release Build please
@dotnet-bot test Outerloop Windows x86 Release Build please

[davidsh]

cc: @MarcoRossignoli

[davidsh]

cc: @Tratcher

[Tratcher]

FYI this has been mitigated in Asp.Net's tests: dotnet/extensions#369. We're not dependent on any changes at your layer, but make sure you get SocketsHttpHandler Host header sorted out eventually.

[davidsh]

FYI this has been mitigated in Asp.Net's tests: dotnet/extensions#369. We're not dependent on any changes at your layer, but make sure you get SocketsHttpHandler Host header sorted out eventually.

@Tratcher
I noticed in dotnet/extensions#369 that you're using the .Authority property. Is that DNS-safe? Why aren't you using .IdnHost which makes sure that the hostname is ASCII characters only and will use Punnycode if there are Unicode characters (which can't be used in HTTP headers such as Host: header)?

Although, it's ironic because Uri.IdnHost has the scope-id in it for IPv6 LinkLocal addresses but doesn't have the square brackets around the IPv6 address.

[Tratcher]

That's only a test client and apparently it's not used for any IDN tests.